Small space heaters, also called portable heaters, are typically used when the main heating system is inadequate or when central heating is too costly to install or operate. Space heater capacities generally range between 10,000 Btu to 40,000 Btu per hour. Common fuels used for this purpose are electricity, propane, natural gas, and kerosene.
Although most space heaters rely on convection (the circulation of air in a room), some rely on radiant heating; that is, they emit infrared radiation that directly heats up objects and people that are within their line of sight.
Combustion Space Heaters
Space heaters are classified as vented and unvented, or "vent free." Unvented combustion units are not recommended for inside use, as they introduce unwanted combustion products into the living space, including nitrogen oxides, carbon monoxide, and water vapor. The units also deplete the air in the space where they are located. Vented units are designed to be permanently located next to an outside wall, so that the flue gas vent can be installed through a ceiling or directly through the wall to the outside.
Electric Space Heaters
For convection (non-radiant) space heaters, the best types incorporate a heat transfer liquid, such as oil, that is heated by the electric element. The heat transfer fluid provides some heat storage, allowing the heater to cycle less and to provide a more constant heat source.
Visit the Energy Saver website for more information about portable heaters in homes.